1. Field of the Invention
The present invention relates to an electrical transmission channel termination device for terminating an electrical transmission channel, and, more specifically, which provides a load impedance to a transmission line matching the line impedance, electrically connects conductors in a monitoring circuit to maintain circuit continuity for detection of incorrect wiring, provides circuits to automatically delete miswiring of AC circuit conductors and electrical short circuits in a transmission line, and provides access for a connection to ground for a conductive shield within a transmission channel.
2. Description of the Prior Art
Electrical transmission lines must be terminated in order for the transmission line to perform efficiently. Typically, an electrical transmission line is terminated using a termination device located at or near the end of the transmission line. In terminating an electrical transmission line it is often necessary to provide an impedance at the termination, referred to as a load impedance, which matches the impedance of the transmission line, or line impedance. Otherwise, a reflection of the transmitted signal back along the transmission line may result, causing communication errors. A typical function of a termination device would be to provide this load impedance. However, termination devices may serve other functions as well. These additional functions will depend on the requirements of the particular transmission line configuration being terminated.
Of particular interest with respect to the present invention is an electrical transmission cable configuration which consists of a single cable or channel containing both conductors which carry data and conductors which supply power. Such a cable may also include a conductor or a foil strip which serves as a shield, separating the power supplying conductors from the data carrying conductors. The shield, when grounded, shields the AC power lines from EMF emissions, which could interfere with other electrical devices, such as AM radios, which are also plugged into the AC power line. The EMF emissions may come from the data conductors and other sources. Such a cable is described in U.S. patent application Ser. No. 07/496,979 filed on Mar. 21, 1989.
Conversely, noise spikes that are present on the power AC conductors are shielded from interfering with data conductors. The invention utilizes the AC ground wire to ground the shield at both cable ends to provide a greater effective shield typically 5-6 db improvement, over grounding at one end only.
The transmission cable configuration described above requires a termination device which can perform several termination functions. Such a termination device was not previously known.